The method for separating a continuous fluid phase from a dispersed fluid is extremely important for industrial applications.
By way of example, this method may involve separating an aqueous phase from an organic phase, such as a crude petroleum phase.
It becomes increasingly important to have an effective method for separating two heterogenous phases of this type. In fact, the concern for protecting the environment makes it necessary to reduce the hydrocarbon content of aqueous waste having extremely low values.
Separation installations, such as those equipping off-shore crude petroleum production platforms, also need to be compact and light to satisfy economic constraints and allow for production in difficult zones. This is even more valid when these separation installations are installed between two water levels or at the water bottom, especially in crude petroleum and gas applications.
Finally, it is essential to use simple reliable methods and devices requiring minimum maintenance and being capable of easy automation.
There are a large number of techniques for embodying such a separation.
The simplest technique consists of sending the mixture of the phases to be separated into a chamber whose volume is calculated so as to enable the mixture to remain there for a sufficient time allowing all the drops or bubbles forming the dispersed phase to have sufficient time to collect together and coalesce at the separation interface between the two phases.
This technique, which is currently widely used, results in requiring the use of installations taking up a large amount of space.
One improvement of this technique consists of having, on an inside of the separation chamber, parallel plates on which the dispersed phase coalesces before rising to the interface for separating the two phases.
Another technique consists of placing a lining which improves coalescence of the dispersed phase.
Another technique, known as flotation, used when the dispersed phase is a liquid phase, consists of making the coalescence dispersed phase rise by sending a fine gas dispersion, the droplets to be separated being fixed on the surface of the bubbles.
The phase separation technique may be significantly improved by resorting to making use of the effect of centrifugal separation so as to increase or replace the effect of gravity. This may be carried out in a centrifugal machine driven by a motor, which makes it possible to embody an extremely compact installation. However, this solution has the drawback of being too complex and less reliable owing to the presence of the motor.
The centrifugal effect may also be obtained in a fully static device. The use of cyclones and especially hydrocyclones based on such a principle is currently being developed due to the advantages possible with such devices allowing for good separation effectiveness whilst being those of the static type.
The inventors have discovered that it is possible to embody a static type separation by a method more effective than known methods of the prior art by coalescing the fluid phase dispersed on a surface whose geometry makes it possible to collect the dispersed phase into one zone and the continuous phase into another zone by submitting both the two phases to be separated to a rotating movement obtained by the flow of the mixture to be separated along the coalescence promoting surface.
More specifically, the method of the invention consists of sending the mixture to be separated into a preferably vertical chamber in which an internal helicoidal surface is disposed whose generating line slants with respect to the perpendicular plane of the chamber axis, thus ensuring the mixture to be separated is rotary-driven and collecting the dispersed particles of the phase on the internal helicoidal surface disposed in the chamber.